1.1 Purpose and Usefulness. Designed specifically to meet the need of television, radio and industrial electronics technicians for a compact, reliable, and simple-to-use instrument for testing capacitors, the Sprague Model TO-6 Tel-Ohmike represents the culmination of years of experience in this field. It incorporates in one instrument an accurate multi-range capacitance and power factor bridge, an insulation resistance checker for paper, plastic-film, mica, and ceramic capacitors, and a leakage current test circuit for electrolytic capacitors. Pushbuttons are provided for instant range selection and a magic-eye tube simplifies bridge balancing for capacitance measurements. A large meter gives direct pointer readings of insulation resistance and leakage current and shows the exact voltage applied to electrolytic capacitors during the leakage test. 1.2 Six especially valuable features of the Model TO-6 Tel-Ohmike are: (I) the I-R (insulation resistance) range of 500 Mil-50 KMii, (2) a special I-R range of 100 Mil-10 KMii (with a 30 volt circuit for low-voltage capacitors), (3) the special low-capacitance bridge circuit for testing low-value ceramic, mica, plastic-film, and air dielectric capacitors from 1-100 pF with improved accuracy, (4) the meter protection which prevents "burn-outs” should the meter be overloaded, (5) the Safety switch for easier discharge of capacitors after test, and (6) the "eye” amplifier to provide greater reading accuracy. 1.3 Capacitance. In addition to the special low range mentioned above, 4 other capacitance ranges are provided for measurements up to 2000 ¿tF. With a TO-6 Tel-Ohmike you are prepared to test every type of capacitor from tiny ceramics or micas to paper and film capacitors of all types, as well as electrolytics—tantalum or aluminum—wet or dry—low voltage or high voltage—small capacitance or large capacitance—from small filter types to large motor-start or photoflash types. 1.3.1 Power Factor. The power factor of all electrolytic capacitors is indicated directly in percent on a single scale. 1.4 Leakage Current. A self-contained continuously adjustable d-c power supply permits measurement of electrolytic capacitor leakage current at exact rated voltage. 1.5 Insulation Resistance. Most paper, plastic-film, ceramic, mica, and air dielectric capacitors have their I-R measured by a circuit which applies 150 volts to the capacitor, and the I-R is indicated directly on the meter dial from 500 Mil to 50 KMii. For testing low-voltage non-elec-trolytic capacitors, an additional range of 100 Mil to 10 KMii is provided in conjunction with a circuit which applies only 30 volts to the capacitor under test. 1.6 Line Voltage and Frequency. The Model TO-6 Tel-Ohmike is available in four types. The standard TO-6 is intended for 115 volt, 50-60 cycle a-c lines. The TO-6RM is similar except that it is intended for mounting in standard 19” relay racks. Also available is the Model TO-6S for use on 115/230 volt, 50 cycle mains. Before using a Model TO-6S, check to see whether the link on the internal terminal plate is in the proper position for the line voltage on which the instrument will be used. A rack-mounting version, the TO-6SRM, is also available.